Window guards designed to discourage thieves or prevent small children from falling through a window are well known. For example, the Canadian Pat. No. 471,248, issued Feb. 6, 1951 to Hawkins et al, discloses "burglar bars" adapted to fit into window frames of different widths, but not necessarily heights. The guard is secured by a set-screw means in a hole covered with putty and paint after installation and needs a special tool for removal.
Another Canadian Pat. No. 507,899, dated Dec. 7, 1954, issued to Montafusco, teaches the use of a relatively complex assembly specifically designed for installation in sash windows.
In the U.S. art, by way of example, the patent to Crandall bearing U.S. Pat. No. 1,954,559, and issued Apr. 10, 1934, makes use of a plurality of twisted vertical bars threaded into horizontal members and kept in place by a barrel-type lock which might be tampered with fairly easily by a thief. Yet another U.S. patent to Hutchisson Jr. bearing U.S. Pat. No. 3,167,828, issued Feb. 2, 1965 discloses a device which is also specifically applicable to sash windows and which can assume only a partial "knock-down" condition when not in use.